1. Field of the invention
The invention is based on a drive for a feed valve having an hydraulically pressurized actuating line and having a device for controlling the pressure in the actuating line which has three valves connected to one another to form an hydraulic auctioneering circuit.
2. Discussion of background
The Patent CH 666 132 discloses a drive for a feed valve. This drive which is operated with oil under comparatively low pressure actuates, for example, a quick-acting gate valve which serves as feed valve for feeding steam into a turbine. The oil under pressure or a different hydraulic fluid acts on the drive via an actuating line so that said drive can open or close the feed valve. The pressure in the actuating line is controlled via a device which has three valves connected to one another to form an hydraulic auctioneering circuit. These valves are constructed as electromagnetically actuated sliding valves and the operativeness of each is monitored separately so that three monitoring circuits are necessary. These monitoring circuits have mechanical contacts which require servicing. This device is less suitable for use at higher pressures.